HF Ccean Radar: from Down-Under to Europe

The Australian Coastal Ocean Radar Network consists of 12 individual radars installed around the coast clockwise from Central Queensland to north of Perth. ACORN was established primarily for research and measuring coastal currents. However, some of the units are monitoring wave heights and wind directions. Some performance results of ACORN are given to illustrate the capability of the technology. The ACORN network operates continually with data being archived in near real time into the IMOS (Integrated Marine Observing System) database, and freely available for research or commercial applications. One of the most important commercial applications of this technology is in monitoring the waters near entrances to ports and harbours

Coastal Ocean Radars: results and applications

A descriptive overview of the Australian Coastal Ocean Radar Network is given with some background about how sites are selected and configured. A suite of results and applications emanating from the ACORN network is presented, including Lagrangian Tracking; assistance to management in the Great Barrier Reef Marine Park; assistance in the salvage of a grounded ship; and the observation of cold fronts in the Southern Ocean

Radar-based tracking of pollutants/larvae in the Coral Sea

A Lagrangian approach is used in physical oceanography to follow a parcel of water as it moves along its flow path and changes shape. Buoyant particles can be tracked to understand and predict the movement of pollution, flotsam and biota on the sea surface. We used data from a high-frequency radar system to compute radar-based Lagrangian trajectories in the Capricorn/Bunker region of the Great Barrier Reef (GBR, Australia). This paper describes case studies for the tracking of flotsam from the Shen Neng I grounding on Douglas Shoal in 2010, and for the destination of coastal waters adjacent Gladstone at the time of a fish disease event in September 2011. Further, the movement of a passive buoyant particle can also be inferred from Lagrangian tracking, which is a valuable technique to study connectivity between reefs. Radar-based trajectories show that wind and tidal conditions greatly affect the advection and spread of particles near the surface in shallow areas of southern GBR, but larger scale processes may be dominant during particular occasions. Therefore, the timing of larval release is crucial to determine the degree of larval retention or advection. We have made a scenario calculation for intermittent release of particles from Heron Island (GBR) for the 2009 spawning to illustrate the capability of the methodology for connectivity research; we also discuss how to couple this with a behavioral model to predict migration paths of larvae

Coastal ocean radars applied to coral reef science and management

Coastal ocean radars provide detailed surface current maps and wind directions; some types of High Frequency radar also provide maps of wave heights. Radar range is dependent upon the radar frequency, extending up to 150 km from the shore. In the case of the Great Barrier Reef, this includes the continental shelf and some open water beyond. Detailed knowledge of the dynamics of the surface water opens the way for understanding much about localised environmental conditions, connectivity between sites and the movement of nutrients and pollution in the coastal ocean. Lagrangian tracking of buoyant particles can be achieved in the Great Barrier Reef lagoon within an accuracy (error) approaching 1 km per day of drift. This is a significant capability for search and rescue operations as well as reef science and management. A sequence of surface current maps has been shown to be useful for identifying areas where the currents are high enough to induce spontaneous turbulence throughout the water column. These areas are less vulnerable to coral bleaching because the heat from insolation is distributed through the water column rather than remaining at the surface. Spatial scales (i.e., range, resolution) for ocean radars are adjustable and it is shown that mapping of surface currents on a high resolution grid is possible with radars operating in the Very High Frequency band

Detection and Warning of Tsunamis Generated by Marine Landslides

Seismic signals provide an effective early detection of tsunamis that are generated by earthquakes, and for epicentres in the hard-rock subduction zones there is a robust analysis procedure that uses a global network of seismometers. For earthquakes with epicentres in soft layers in the upper subduction zones the processes are slower and the seismic signals have lower frequencies. For these soft-rock earthquakes a given earthquake magnitude can produce a bigger tsunami amplitude than the same earthquake magnitude in a hard rock rupture. Numerical modelling for the propagation from earthquake-generated tsunamis can predict time of arrivals at distant coastal impact zones. A global network of deep-water pressure sensors is used to detect and confirm tsunamis in the open ocean. Submarine landslide and coastal collapse tsunamis, meteo-tsunamis, and other disturbances with no significant seismicity must rely on the deep-water pressure sensors and HF radar for detection and warning. Local observations by HF radar at key impact sites detect and confirm tsunami time and amplitude in the order of 20–60 minutes before impact. HF radar systems that were developed for mapping the dynamics of coastal currents have demonstrated a capability to detect tsunamis within about 80 km of the coast and where the water depth is less than 200 m. These systems have now been optimised for tsunami detection and some installations are operating continuously to provide real-time data into tsunami warning centres. The value of a system to warn of hazards is realised only when coastal communities are informed and aware of the dangers

High Resolution Ocean Radar Observations in Ports and Harbours

Observations are shown from an ocean radar system which operates in the VHF frequency band (100-180 MHz) and produce surface current measurements on grid scales of 50-200m over ranges up to 6-10 km. This is a scale of operation that is well suited to measurement tasks in Ports, harbours and coastal zones. Ocean radars commonly used for mapping surface currents in coastal zones operate in the HF frequency band and measure currents on grid scales of 3-6 km over distances of 100-200km. The VHF ocean radar system consists of two stations which look at the same patch of ocean from different directions. Each station measures the radial component of the surface current at each grid point, and by combining data from both stations it is possible to produce maps of surface current vectors. Each station can cover a 60-degree sector of azimuth, and for wider coverage it is possible to use multiplexed receive antennas to double the size of the sector. The time to make the basic 60-degree sector for two stations is 10 minutes, and becomes 20 minutes for the wider 120 degree coverage. Results are shown for sheltered coastal waters and for open coast line where there are breaking waves. This methodology is particularly appropriate for monitoring currents in congested port areas where fixed moorings may be compromised

Multi-hazard management of coastal zones supported by HF radar

HF radars have been installed in many coastal sites around the world to monitor ocean parameters between the coast and maximum of about 250 km offshore. The main product of phased array radars is gridded maps of surface currents, wave heights and wind directions. Maps of surface currents (see Figure 1) can be produced every 10 – 20 minutes which, in real-time, improve navigation safety in restricted areas commonly found near ports and harbours. The time-sequence of surface current maps enables Langrangian tracking of small parcels of surface water. This analysis of the data is being used for hazard mitigation in managing suspended sediments in dredging, in emergency situations where flotsam and other drifting items need to be found, and in pollution control. Additionally the surface current measurement capability is used to assist tsunami warnings. The newly launched Tsunami Warning Center in Oman includes a network of phased-array HF radars to provide real-time tsunami monitoring. Real-time mapping of significant wave heights is being used to improve operational safety for coastal shipping and small boats. Long-term records of wave heights are needed for managing the coastal environment. Wind direction maps are being used to locate the position of cold fronts in the open ocean and to monitor the timing and strength of sea-breeze fronts in key locations. This paper presents case studies showing how HF radars are currently being used for monitoring these ocean parameters at various sites around the world. The oral presentation will end with an example of hazards whose impact could be reduced with an HF radar installation

Measurement of Electrical Conductivity for a Biomass Fire

A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K

Application of HF Radar in Hazard Management

A review is given of the impact that HF radars are having on the management of coastal hazards. Maps of surface currents can be produced every 10 – 20 minutes which, in real-time, improve navigation safety in restricted areas commonly found near ports and harbours. The time-sequence of surface current maps enables Lagrangian tracking of small parcels of surface water, which enables hazard mitigation in managing suspended sediments in dredging, in emergency situations where flotsam and other drifting items need to be found, and in pollution control. The surface current measurement capability is used to assist tsunami warnings as shown by the phased-array data from Chile following the Great Tohoku Earthquake in 2011. The newly launched Tsunami Warning Center in Oman includes a network of phased-array HF radars to provide real-time tsunami monitoring. Wind direction maps can be used to locate the position of cold fronts in the open ocean and to monitor the timing and strength of sea-breeze fronts in key location

Relating Best Practices to Standardization in Ocean Science

Over the past decade, the Ocean Best Practices System, hosted and maintained by the International Oceanographic Data and Information Exchange of UNESCO's Intergovernmental Oceanographic Commission, has grown to become a trusted and stable repository for all types of ocean Best Practices documentation. Given the nature of the information it contains, the repository embodies a unique resource base for supporting initiatives aimed at strengthening standardization in Ocean Science. Based on this consideration, the Ocean Best Practices System is forming a new task team to explore and evaluate the potential role that the comprehensive Best Practice information it secures could play in identifying and prioritizing processes for furthering this objective. Particular care is being taken to keep the work open and transparent through constant community engagement and by linking with international bodies/organizations dealing with measurement